Preparation of anthraquinone diacridones



PREPARATION OF ANTHRAQUINONE DIACRIDONES Lynne H. Ulich, Woodstown, N. J., assignor to E. l. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware I No Drawing. Application May 11, 1954, Serial No. 429,105

5 Claims. (Cl. 260-276) a continuation-in-part of my co- N. 290,573, filed May 28, 1952,

This application is pending application S. now abandoned.

This invention relates to the preparation of anthraquinone diacridones from 1,5-dianilido-o,o-dicarboxylic acid by ring closure, and more particularly by ring closure with benzoyl chloride and phosphoric acid.

Heretofore, ring closure of anilido anthraquinones to acridones for use as a vat has been accomplished by several different processes. In U. S. Patent 961,048 to Ullmann, ring closing was effected by the use of sulfuric acid or by treating the anthraquinone dianilido carboxylic acid with phosphorus pentachloride, and then closing the ring with aluminum chloride. In U. S. Patent 2,449,011, a method is disclosed for ring closure to form acridones in which sulfuric acid is also used. This method, however, has the disadvantage that considerable sulfonation of the aromatic ring takes place with a correspondingly reduced yield. It will be apparent, therefore, that a method which. produces the diacridone without undesirable side reactions or sulfonations would be highly desirable.

It is therefore an object of the present invention to provide an improved economical process for converting anthraquinone-l,5-dianilido-o,o-dicarboxylic acid to the phosphoric acid in nitrobenzene at a temperature of about 150 to 170 C., and then isolating the anthraquinone diacridone. The process is carried out within rather critical molar ratios, namely one mol of anthraquinone-1,S-dianilido-o,o'-dicarboxylic acid, from 3.3 to 4.0 mols of benzoyl chloride, and from about 0.20 to 0.70 mol of phosphoric acid. The molar ratio of phosphoric acid to the anthraquinone carboxylic acid is particularly critical. Less than about 0.20 mol produces low yields, and more than 0.70 mol of phosphoric acid results in an inferior dye. The preferred ratio of phosphoric acid is about 0.45 mol per mol of anthraquinone- 1,5-dianilido-o,o'-dicarboxylic acid, and this molar ratio yields about 80% to 85% of the theoretical yield of the diacridone.

tion to the dicarboxylic acid chloride must be carried out at temperatures around 70 to 75 C., and then the reaction mass must be heated to about 160 to 170 C. to complete the ring closure.

The preferred solvent is nitrobenzene, although it has 2,726,242 Patented Dec. 6, 1955 been found that trichlorobenzene is also effective .and is the full equivalent of nitrobenzene. Other solvents :in which thereactants. and reaction product are soluble, and whichareinert to the reactants and catalysts at 170 and which boil above this temperature, may likewise be used under some circumstances.

The following examples are given to illustrate the invention, but no limitation is intended to be placed thereon except as defined in the appendedclaims.

' "Example I 65.0 parts of anthraqu'inone-1,5-dianilidoo,0-dicarboxylic acid of 97.5 purity is charged into an agitated and jacketed vessel containing 650 parts of dry nitrobenzene .and7.06 parts. of orthophosphoric acid (equivalent to 6.0 parts of acid). The mass is agitated and heatedito to C. for one hour to remove any free water. The mass is then heated to i while 62.1 parts of benzoyl chloride is addedat a uniform rate over a period The temperature is held at 150 to 160 while the mass is agitated. Gaseous hyis evolved as the reaction proceeds. The reaction mass is then cooled to 100 to 120 C. and filtered. The filter cake is washed with 650 parts of nitrobenzene at 80 to 100 C. The last Wash liquor is only slightly pink.

The filter cake is transferred to a steam distillation vessel, sufiicient sodium carbonate is added to make the mass alkaline and it is steam distilled until no more nitrobenzene distills off. The charge left in the still is then filtered and washed with hot water until it is free of alkali. The filter cake is dried at 100 to 105 C. There results 48 parts of anthraquinone diacridone which is an 80% yield.

Examples II to V1 The process of Example I was repeated except that the amount of phosphoric acid was varied. The results are shown in the table below and the data of Example I preferred embodiment of the 80% of the theoretical yield This example was repeated Without and a yield of about 58% was obduction in the percentage yield of the diacridone will be found.

The present invention offers many advantages. For example, if sulfuric acid is used as a catalyst with nitrobenzene as a solvent at temperatures required for the formation of the ,diacridone in good yields, sulfonation of the aromatic rings occurs, together with a decrease in yield and with formation of tar and other discoloration. In the present invention these undesirable products are avoided. .The anthraquinone diacridone prepared according to the present invention is a valuable vat dye, and when cotton is dyed with it by conventional methods, a violet color is obtained having excellent clarity.

It is apparent that many widely difierentembodiments of this invention may be made without departing from the spirit and scope thereof, and therefore, it is not intended to be limited except as indicated in the appended claims.

I claim:

1. The method of preparing anthraquinone diacridones which comprises heating in proportion one mol of anthraquinone-l,S-dianilido-o,o'-dicarboxylic acid with a ring closing agent consisting essentially of from 3.3 to 4.0 mols of benzoyl chloride, and from about 0.20 to 0.70 mol of phosphoric acid in nitrobenzene at 150 to 170 C. for at least six hours, and thereafter isolating the anthraquinone diacridone so produced.

2. The process of phosphoric acid is about 0.45.

claim 1 in which the molar ratio of 3. The process of claim 1 in which the molar ratio of benzoyl chloride is about 3.5.

4. The process of claim 1 in which the temperature is from 160 to 165 C. and is maintained for about 6 to 7 hours.

5. The process which comprises heating about 65.0 parts of anthraquinon -1,5-dianilido-0,o'-dicarboxylic acid with 650 parts of nitrobenzene and 6 parts of orthophosphoric acid at a temperature of to C. for about to C.

parts of benzoyl chloride slowly, maintaining the temperature for about 6 hours, cooling the reaction mass to about 100 to 120 C., filtering, and Washing the filter cake with nitrobenzene at about 80 to 100 C., steamdistilling the washed filter cake to remove any occluded nitrobenzene, washing the retained charge, and thereafter drying at about 100 to 105 C.

References Cited in the file of this patent 

1. THE METHOD OF PREPARING ANTHRAQUINONE DIACRIDONES WHICH COMPRISES HEATING IN PROPORTION ONE MOL OF ANTHRAQUINONE-1,5-DIANILIDO-O,O''-DICARBOXYLIC ACID WITH A RING CLOSING AGENT CONSISTING ESSENTIALLY OF FROM 3.3 TO 4.0 MOLS OF BENZOYL CHLORIDE, AND FROM ABOUT 0.20 TO 0.70 MOL OF PHOSPHORIC ACID IN NITROBENZENE AT 150* TO 170* C. FOR AT LEAST SIX HOURS, AND THEREAFTER ISOLATING THE ANTHRAQUINONE DIACRIDONE SO PRODUCED. 